It is well known that artwork is viewed as an important developmental tool for children. For example, marking materials, such as paints and markers, are given to children for drawing, painting, and coloring purposes in order to stimulate their creativity and imagination. Of course, a significant drawback with conventional marking materials is that they tend to become very messy in use. Indeed, parents often limit the use of marking materials by children because of the possibility that household objects, such as carpets and furniture, as well as skin and clothing, would be stained by the marking materials.
Marking systems have been developed that inhibit the formation of inadvertent stains on household objects or other unintended surfaces during use. For example, one commercially-available marking system, which is described in U.S. Pat. No. 6,124,377, provides a marking composition comprising at least one color precursor in the form of a leuco dye, and a substrate provided with a coating comprising at least one color-triggering developer. Upon application of the leuco dye to the substrate, a chromophore, and hence, color, is formed. Application of the leuco dye to the substrate only causes the appearance of color in the areas of the substrate that are coated with the color-triggering developer. One drawback of this marking system is that the user can typically see and/or feel which areas of the substrate are coated, thus it is not surprising which areas will develop color. A second drawback is that artwork for printing the developer coating is typically engraved on an expensive printing cylinder, which is time-consuming and requires a high capital investment. There exists a need for products that are more efficient to manufacture, and that improve upon these marking systems so that the user cannot easily see or feel which areas of the substrate will develop color.